Thermofluid

8) If the pressure, Px, is 75 kPa, find the pressure, Py, in the adjoining water pipe.

9) Determine the required property for water. Interpolate as needed.

10) A 2500 L rigid tank contains 50 kg of air at a temperature of 50°C. Heat is added until the pressure is doubled. What is the final temperature inside the tank?

11) 3 kg or steam initially at 375 kPa and 141.3°C is contained in a piston-cylinder with a diameter of 88 cm. A spring, that is attached to the piston cylinder and initially at equilibrium at a piston height of 160 cm from the bottom, has a spring constant of 128,450N/m. If the piston raises to double its initial height, find the heat input into the steam.

The interior space of a building in winter is to be heated by a heat pump to maintain the internal temperature at 22.0°C. The 55.0 kW building heat load is to be provided by a heat pump that absorbs heat from a geothermal water source at 18.0°C. The water from the geothermal water source enters the evaporator heat exchanger at 18.0°C and exits at 11.00°C. The heat pump utilises refrigerant R-134a as the working fluid and operates with a discharge pressure of 1.40 MPa and a suction pressure of 320 kPa. Modelling the heat pump cycle as an actual vapour compression cycle (AVCC), with an evaporator exit temperature of 10.00°C and condenser entry and exit temperatures of 80°C and 30°C respectively, determine: What is the COP of this AVCC system? b. Determine mass flowrate of refrigerant (in kg/s). Find the required volumetric flowrate of water from the geothermal source (in L/min) d. Determine the isentropic efficiency of the compressor (assume the compressor to be adiabatic). e. If the heat pump were replaced by an ideal Carnot heat pump what would be the required power input to the heat pump? (Assume the heat load is still 55.0 kW).

Bernoulli’s Equation Applied to a Convergent-Divergent Passage

1- Superheated steam at 1.5 MPa (15 bar), 600 °C enters a well-insulated turbine. The exit pressure is 70 kPa (0.7 bar). The turbine produces 10 MW of power. If the exit pipe is 1.6 m in diameter and carries 11 kg/s of flow, find the velocity at the exit. Neglect kinetic energy.

2- Consider natural gas with a molecular weight of 23.6 kg/kmol and a specific heat, c, of 2.01 kJ/kg K. The gas is slowly compressed in a frictionless, adiabatic process from an initial volume of 212 cm? to a final volume of 98 cm?. If the initial pressure is 39 kPa, and the initial temperature is 15 °C, find the final temperature and pressure. Assume the mixture can be modeled as an ideal gas.

1) The superheated water vapor is at 15 MPa and 350°C. The gas constant, the critical pressure, and the critical temperature of water are R = 0.4615 kPa m³/kg-K, Tcr= 647.1 K, and Pcr= 22.06 MPa. Use data from the steam tables. a) Determine the specific volume of superheated water based on the ideal-gas equation. b) Determine the specific volume of superheated water based on the generalized compressibility chart. c) Determine the specific volume of superheated water based on data from tables. d) Determine the error involved in the first two cases (a and b).

2) Air is compressed by an adiabatic compressor from 95 kPa and 27°C to 600 kPa and 277°C. Assume variable specific heats and neglect the changes in kinetic and potential energies. a) Determine the isentropic efficiency of the compressor. b) Determine the exit temperature of air if the process were reversible.

3) A steam turbine operates with 1.6 MPa and 350°C steam at its inlet and saturated vapor at 30°C at its exit. The mass flow rate of the steam is 21.8 kg/s, and the turbine produces 12,350 kW of power. Determine the rate at which heat is lost through the casing of this turbine.

(2) Using example 1-5 as a guide, find Q1, Q2 and PB for L1= 1200 m P= 758 kPa L2=1200 m. D1-30 cm (0.3 m) ZA-36 m D2=20 cm (0.2 m), 1=3x10 m 2= 3x105m, ZB= 25 m. QA= 0.17 m³/s, p(density)=1000 kg/m² v/kinematic viscosity)=10€ m²/s

(a) A water tank is completely filled with liquid water at 60rc. The tank material is such that it can withstand tension caused by a volume expansion of 4%. Determine the maximum temperature rise allowed without jeopardizing safety. Take water coefficient expansion (B) as 5.22 x 10*1K at this temperature. (b) A weight, as shown in figure Qib-(a) has to move at constant velocity of 2 m's on an inelined surface with a coefficient of friction of 0.27. The width of the block is 20 cm. Determine the force (FI) that needs to be applied in the horizontal direction. By applying a thick oil film as shown in figure Qlb-b), the force required to push the block reduced by 45%. If dynamic viscosity of the oil is 12 cP,determine the oil layer thickness. (c) A gate with 2 m width is kacated under the water as shown in Figure Qlc. IF the force(F) required to held the gate is about 20 kN, determine the distance (dj of this force to

a) Given that for a flew process the steady flow equation is: q-w=\left(u_{2}-u_{1}\right)+\left(p_{2} v_{2}-P_{1} v_{1}\right)+\left(\frac{C^{2}}{2}-\frac{C_{1}^{2}}{2}\right)+p\left(x_{2}-z_{1}\right) b) Explain how the following jet engine works. Refer to each section of the engine and explain the purpose of each section. e) Draw a Temperature (T) versus Entropy (s) diagram for a typical gas turbine. The diagram should show the processes for an actual gas turbine and should show the effect of real world losses where the compressor and turbine have an isentropic efficiency and pressure losses in the combustion chamber in an actual gas turbine.Explain each of the processes on the T-s diagram.

Question 3 A large horizontal brass plate is used to boil water at atmospheric pressure. What is the maximum permitted temperature of the plate so that it does not exceed the critical heat flux? [8 marks]

This is an individual assignment, and is worth 30 marks in total. You will need to answer all questions, and you need to bear in mind that in some instances you may need to use knowledge you have previously gained in other courses to solve these questions. Please submit your assigment online. Typed solutions are recommended, but clearly presented hand-written solutions will also be accepted. This assignment is due on 8th October at 11pm. If you submit your assignment late, you will be deducted 4 marks (i.e. 20%) per day that you are late. Question 1 Sheets of steel are typically made by rolling heated steel at high temperatures, resulting in a flat plate as shown in figure 1. The resulting hot flat plates are cooled by passing air at a fixed temperature of 295 K over the plate. The plate is 4 m long, and 1.2 m wide, and has a uniform temperature of 600 K. The velocity of the flow of air is 9.5 m/s. Air 4 m Figure 1: Flow of air over a flat plate. Assuming the sheets are oriented such that the air flow along the length of the plate (i.e., along the a direction, as denoted by the blue arrow), calculate: a) The local heat transfer coefficient at a distance 1 m from the leading edge of the plate (i.e. at x = 1 m) [4 marks] b) The average heat transfer coefficient over the entire plate [3 marks] c) The rate of heat transfer from the plate to the air. [1 mark] If the plate is re-oriented such that the flow of air now flows along the width of the plate (i.e. along the y direction, as denoted by the red arrow), calculate the rate of heat transfer from the plate to the air. [4 marks] In all cases above, you may neglect any heat transfer from the bottom of the plate.